The effects of stimulus duration on ABR and behavioral thresholds.

ABR and behavioral thresholds were estimated as a function of stimulus duration for three normal and two hearing-impaired subjects. Stimuli were 2000-Hz tone bursts with 0.5-ms rise/fall times and durations ranging from 1 to 256 or 512 ms. For both groups of subjects, ABR thresholds were independent of stimulus duration. Normal subjects showed greater improvement in behavioral thresholds as a function of duration than did subjects with hearing losses. Thus, it appeared that ABR and behavioral thresholds were affected differently by changes in stimulus duration and that the magnitude of these differences could depend upon the presence of hearing loss. These data indicate that temporal integration may be one factor which makes comparisons between ABR and behavioral thresholds complicated. In the present study, the magnitude of hearing loss, measured by the ABR, would have been underestimated if normal behavioral thresholds for short-duration stimuli were used as the reference.